In Chinese tradition the east wind blows in spring, so
东风 is poetically synonymous with renewal and good fortune — the opposite of the cold, bleak
西风 'west wind.' The phrase
万事俱备,
只欠东风 ('everything is ready, only the east wind is lacking') comes from the Battle of Red Cliffs in 《
三国演义》, where Zhuge Liang allegedly 'borrowed' an east wind to enable the famous fire attack on Cao Cao's fleet.